Electronic discharge device for electronic multiplication



ELECTRONIC DISCHARGE DEVICE FOR ELECTRONIC MULTIPLICATION Filed Aprl'l, 1945 Feb. 22, i949. M ARDn-l 2,462,059

Patented Fei. 22, 194e ELECTRONIC DISCHARGE DEVICE FOR ELECTRONIC MUL'IIILIQATION Maurice Arditi, Boulogne-Blllancourt, France, asvsignor to International Standard Electric Corporation, New York, N. Y., a corporation of Delaware .Appiicatin April-'1, r1943, serial Nu. 481,509

' In France July 25, 1941 Section 1, Public Law 690, August 8, 1946 Patent expires July 25, 1961 are multiplied by successive secondary emissions,v

to control the primary and secondary electronic beams by means of an electric field which accelerates the electrons as they leave an emitting electrode and of a magnetic field which deects each electron beam toward the next emitting or col- 7 Claims. (Cl. 25o-175) lecting electrode. For this purpose, generally, a

series of non-emitting electrodes is associated with a series of primary and secondary-emission electrodes and the distribution of- .potentials between these series of emitting and non-emitting electrodes is such that it creates, in the space in front o f the electrodes, electric potential gradientsaiding the extraction of secondary electrons from the various targets under the impact of electrons from the preceding target. A transversal magnetic eld is applied in this space to deect the electrons emitted by one target towards the next target. The acceleration and deflection of the electrons are generally obtained simultaneously through the combined action of the two electric and magnetic elds.

The electric potential gradients required for driving the emitted electrons from stage to stage are, as a rule, not uniform between the various emitting and acceieratin'g electrodes. This entails a dispersion of electrons which is harmful to the eilciency of the device owing to the defocusing of the electronicpaths, and on the other of the electrons.

These and other objects are accomplished, ac-

drawings, in which cording to the invention, by the arrangement and combination of elements set forth in the following description, deilned in the appended claims and Illustratively exemplied in the accompanying Fig. 1 is a diagram of an electron multiplier device, according to the invention, from which most of the details of physical construction, the vessel, the supporting connections of the electrodes, the magnet or electromagnet furnishing the transversal magnetic eld and other elements which are not necessary for an undertaking of the in- `vention, have been omitted for the sake of sim- Dlicity;

Fig. 2 is a further simplified diagram of a modied structure v Fig. 3 is a perspective view, certain parts being broken away or shown in section, of a third embodiment of an electron multiplier according to the invention, no electrical connections inside of the tube being shown in this'figure;

Fig. 4 is a perspective view of the screen 5a of the electron multiplier of Fig. 3 showing details of the invention.

Referring now to the drawing, and first to Fig. v1, a photo-cathode l is arranged in a common plane with two secondary-emission electrodes or targets 2 3, and a collecting electrode 4. An electric screen in the form of a box 5 is placed in front of the electrodes I to 4. The screen box 5 consists of a non-magnetic metal so that a transversal magnetic field H may cross it. It is provided with two aligned openings 6 and 6', 'in its front and rear walls, respectively, opposite the photo-cathode I, to allow passage 'of a lightbeam 1, and with three additional openings 8, 9 and I0 in its front wall opposite the secondaryemission electrodes 2 and 3 and the collecting electrode 4, respectively, to allow passage of the electronic beams. A high electric potential is4 applied to the entire box 5, so that a zero potential gradient region lls created within the box. l

The potentials to which the various electrodes are raised may be taken from a single potentiometer Il in the manner shown. The collecting electrode 4 is raised to the same high potential as the screen box 5, and may even be constructed as a part of such box.

The photo-cathode l is surrounded by a Wehnelt cylinder orA other auxiliary electrode l2, and

3 the secondary-emission electrodes 2 and 3 are associated with Wehnelt cylinders, Il and Il, respectively. 'I'hese auxiliary electrodes which serve for the concentration and acceleration of outgoing electrons (or for the deceleration of incident electrons) are raised to suitable potentials taken from the potentiometer Il. The auxiliary electrodes i2 and Il are raisedpreferably to the same potential. The relative potentials of the 'various electrodes are preferably so chosen that the impact speeds of the incident electrons on the secondary-emission targets insure a maximum extraction of secondary electronsv from thelatter. These impact speeds expressed in volts correspond generally'to potentials of 500 to 700 volts.

It will be understood that any more or less complex electron-optic structure may be associated with each emitting electrode for the concentra.- tion and speed regulation of the electrons.

Means (not shown) are provided to apply to the zero electric potential gradient region within the box l a transversal magnetic iield H which, in this zero potential region, acts only to deflect the electronic beams from one electrode to the next one. Within the box 5, the electronic beams follow substantially circular paths. No acceleration or deceleration takes place within this box, and, therefore, the interfering ions or electrons emitted by the photo-cathode are unable to pass directly to the collecting electrode l. The residual current of the device is very small and there is no "obscurity current on the collecting electrode 4. Any possible contamination of the secondary-emission electrodes 2 and 3 by a direct evaporation of the cathode decomposition products is completely obviated.

'I'he electronic iiux from the cathode I may be additionally controlled by a grid I of usual construction.

Instead of a closed screen box such as 5 (Fig. 1), a screen consisting simply of two spaced apart, suitably perforated, parallel plates I6 and I1 may be used, as shown in Fig. 2. The structure of Fig. 2 is similar to that of Fig. 1 and the same reference characters are used for the corresponding elements. The two screen plates I8 and I1 are raised to the same electric potential, for example by means of a connection I8, so that the electric potential gradient is zero in the region between the two plates I6 and I1 where the deiiecting magnetic ileld H is applied. The operation of the device is, thus, similar to that of the structure of Fig. 1 and its advantages are substantially equivalent.

In Fig. 3, the screen 5a is cylindrical and it is surrounded by two likewise cylindrical grids and 2I. Grid 2li acts as a Wehnelt electrode for all the secondary-emission electrodes 2 and 3 and for the collecting electrode I. The photo-cathode Ia is associated with an individual Wehnelt cylinder 3| serving as a control electrode. Grid 2l acts as an accelerating grid (for the outgoing electrons) and as a decelerating grid (for the incident electrons). 'I'he two grids 20 and 2| are deformed at the locations corresponding to the emitting and collecting electrodes in the manner shown at 22, 23, 2l and 25 for grid 2li, in order to produce at these points electronic-lens eiects for concentrating and focussing the emitted and received electrons. The cylindrical screen 5a has perforation 6a, 8a, la, Ita similar to those of the box 5. This is illustrated in Fig. 4. Within the perforated cylinder screen 5a the electric potential gradient is kept at zero as inthe case of the box or theplates of Figs. 1 and 2, respectively,

and the transversal magnetic field H'is applied in this region by means of a magnet 20, the pole pieces of which surround the structure in the manner shown. Fig. 3 shows, partly cut away, the insulating enevelope 21 of the structure, its socket base 2l and the connector plugs 2|.

Further, as a modincation of the secondaryemission electrode arrangement, Fig. 3 shows, by way of example, the secondary emission electrodes 23 and 24 formed ona single curved plate 3l, which reduces the number of plugs 2t. A control grid IS may be associated with photo-cathode la as shown.

It is obvious that the invention is not limited to the examples shown and described but is capable of numerous modifications and -variations within the scope of the following claims.

I claim:

1. An electronic discharge device for secondary emissions comprising a. primary emitting electrode, a secondary emitting electrode, and a collecting electrode, all said electrodes being mounted in succession and substantially aligned, electrode means mounted in front of said aligned electrodes for producing a zero potential gradient region beginning a short distance from said aligned electrodes and extending along the path of the electron beams emitted by said aligned electrodes, said electrode means having apertures for the passage therethrough of the electron beams, means adjacent said aligned electrodes and in the short space between said aligned electrodes and said region of zero potential gradient for controlling the speed of the electrons in said beams, and means adjacent said region of zero potential gradient for applying therein a transverse magnetic iield for the deflection of the electron beams entering said region.

2. An electronic discharge device as claimed in claim 1 in which said means for controlling the electron speed comprises regulating electrodes adjacent the individual emitting and collecting electrodes respectively for regulating the speed of and concentrating the emitted electrons.

3. An electronic discharge device, as claimed in claim 1 in which said aligned electrodes are substantially in a common plane and said means for producing a zero electric potential gradient region includes two spaced parallel plates consisting of an electrically conductive non-magnetic material, said plates being mounted rearwardly of one another in front of and parallel to said common plane, the plate next to said plane being provided with openings opposite said electrodes to permit the passage of electronic beams into the space between said plates.

4. An electronic discharge device `for secondary emissions. comprising a primary emitting electrode, a. secondary emitting electrode and a collecting electrode, said electrodes being disposed side by side on a generatrix of an imaginary cylinder, a screen-cylinder defining a zero electric potential gradient region consisting of an electrically conductive, nonmagnetic material and having substantially the same axial length but a smaller diameter than said imaginary cylinder, said screen cylinder being located concentrically within said imaginary cylinder in front of said electrodes and being provided with openings opposite the latter, respectively, and means adjacent said region for applying therein a transversal magnetic field for the deflection of the electron beam entering said region.

5; An electronic discharge device, as yclaimed in claim 4 in which said means for controlling the electron speed comprises, between said screen cylinder and said imaginary cylinder', concentric grids deformed at points opposite said electrodes constituting electron concentrating and electron speedregulating elements for the various emitting and collecting electrodes, respectively.

6. An electronic discharge device according to claim 1 in which the means for creating a Zero potential gradient region comprises two metallic members having substantially all corresponding vportions of their adjacent surfaces spaced equitant from one another.

.l 7. An electronic discharge device according to claim 1 in which the means for applying a magnetic field comprises a generator of magnetic flux located adjacent the zero potential gradient region for applying in said region a transversal magnetic eld for the deliection by substantially 180 of the electron beams entering said rleon.

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Emma' ENCES CIT The following references are of record in the le of this patent: 

